The present invention relates to a cement dispersant and a concrete composition containing the dispersant. In more detail, the present invention relates to a cement dispersant having superior dispersion effect of cement particles and its retention, thereby obtaining greater water-reducing effect and long slump flow retention, so that a workability is excellent and strength development after hardening is good, particularly a cement dispersant suitable for concretes with ultrahigh performance, and a concrete composition such as an ultrahigh performance concrete composition containing the dispersant.
Polycarboxylic acid type dispersants such as a copolymer of polymelamine sulfonate, lignin sulfonate, olefin and maleic acid and the like have conventionally been used as a cement dispersant. However, these compounds have problems in not only their effect connoting as slump flow retention effect, but their suitability in existing as well as future ultrahigh performance concrete.
New type polycarboxylic acid type cement dispersants having nonionic groups introduced therein are positively proposed to solve these problems. For example, JP-A 1-226757 discloses a copolymer of (meth)acrylate, (meth)acryl sulfonate, and monoacrylate ester of polyethylene glycol alkyl ether or monoacrylate ester of polypropylene glycol alkyl ether. However, conventional cement dispersants including the one disclosed in the above publication have not yet been satisfactory as to all of water reducing effect, slump flow retention, strength development and the like in order to use as a compounded concrete with said dispersants.
Therefore, there is a strong call in the industry for cement dispersants meeting sufficient water reducing effect, slump flow retention, strength development and the like, applicable even to ultrahigh performance concrete.
The present invention has been made to meet this demand, and has an object to provide a cement dispersant with satisfactory water reducing effect, slump flow retention, strength development and the like, and a concrete composition containing said dispersant in order to solve the problems existing in the prior art.
After extensive investigation into finding the solution for the problems, the present inventors have found a copolymer comprising three specific organic substances with the desired effect, and have completed the present invention as described.
That is, the present invention relates to a cement dispersant comprising a water soluble amphoteric copolymer, as a main component, obtained by copolymerizing an addition product(compound A) obtained by the addition of 0-8 moles of an alkylene oxide having 2 to 4 carbon atoms to one equivalent of amino residues in polyamide polyamine obtained by condensation of 1.0 mole of a polyalkylene polyamine, 0.8-0.95 mole of a dibasic acid or an ester of the dibasic acid with a lower alcohol having 1 to 4 carbon atoms, and 0.05-0.18 mole of acrylic acid or methacrylic acid, or an ester of acrylic acid or methacrylic acid with a lower alcohol having 1 to 4 carbon atoms, and a compound (compound B) of the formula I: 
(wherein R is hydrogen atom or methyl group, and M is hydrogen atom, alkali metal, ammonium group or alkanolammonium group), and a compound (compound C) of the formula II: 
(wherein Rxe2x80x2 is hydrogen atom or methyl group, R1 is C2-C4 alkylene group, R2 is hydrogen atom or C1-C4 alkyl group, and m is an integer of 1 to 100), in the ratio of compound A:compound B:compound C=10-40% by weight:10-40% by weight:50-80% by weight.
The present invention also particularly relates to said cement dispersant of the present invention used in an ultrahigh performance concrete composition.
The cement dispersant of the present invention can also be used as a general purpose high performance AE water reducing agent by blending techniques available for regular concrete.
The present invention further relates to a concrete composition characterized by having said cement dispersant of the present invention, and particularly the concrete composition for an ultrahigh-performance concrete. The xe2x80x9cultrahigh performance concretexe2x80x9d described herewith denotes concrete generally used and understood in the pertinent art, and encompasses concretes in considerably broad range, and includes, for example, concrete showing strength equal to or higher than the conventional concrete even when less amount of water is used as compared with the conventional concrete, or more specifically concrete that provides a highly workable ready-mixed concrete without interfering in general use even when a water/binder ratio is 20% or less, particularly about 12%, and yet with a compression strength of 150 N/mm2 or more upon hardening.
As described above, the compound A used in the present invention is an addition product obtained by the addition of specific amount of an alkylene oxide (compound d) to the polyamide polyamine achieved by condensation of a polyalkylene polyamine (compound a), a dibasic acid or an ester of the dibasic acid with a lower alcohol having 1 to 4 carbon atoms (compound b), and acrylic acid or methacrylic acid, or an ester of acrylic acid or methacrylic acid with a lower alcohol having 1 to 4 carbon atoms (compound c), in a definite proportion.
Examples of the polyalkylene polyamine of the compound a include diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, dipropylene triamine, tripropylene tetramine and tetrapropylene pentamine, but diethylene triamine and triethylene tetramine are preferable from both points of effectiveness and economical angle.
Examples of the dibasic acid and its lower alcohol ester having 1 to 4 carbon atoms of the compound b include, for example, malonic acid, succinic acid, fumaric acid, maleic acid, glutaric acid, adipic acid, pimelic acid, phthalic acid, azelaic acid, sebacic acid, and their esters with lower alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol or butanol, or their isomers, if present. Of those, adipic acid is most preferable from both effectiveness and economical angle.
Examples of acrylic acid or methacrylic acid and its lower alcohol ester having 1 to 4 carbon atoms, of the compound c include, for example, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate and butyl methacrylate.
The polyamide polyamine comprising three components of the above compounds a, b and c can easily be obtained by the conventional polycondensation technique.
The alkylene oxide having 2 to 4 carbon atoms, which is the compound d, to be added to amino residue of polyamide polyamine is ethylene oxide, propylene oxide or butylene oxide. One or more of alkylene oxides described may be used.
Preparation of the polyamide polyamine, inter alia, polycondensation reaction of the compounds a, b and c, may be two-step reaction comprising polycondensation of only the compound a and the compound b, thereafter further polycondensation with the compound c as a monobasic acid, or one step reaction comprising simultaneous polycondensation with the compounds a, b and c from the start.
However, either method leads to the same polycondesation reaction, that is amidation reaction in which acrylic acid residue or methacrylic acid residue of the compound c are ultimately found at the end of a polyamide chain since the amidation reaction proceeds in parallel to amide interchange reaction.
Following is a reaction molar ratio of the three components constituting the polyamide polyamine described below.
The reaction molar ratio of the compound b (dibasic acid or its ester) to one mole of the compound a (polyalkylene polyamine) is 0.8-0.95 mole. Polycondensation product of the compound a and the compound b in molar ratio defined above produces, on the average, a polyamide with a certain chain length, comprising polycondensation of from (polyalkylene polyamine 5 moles:dibasic acid 4 moles) to (polyalkylene polyamine 20 moles:dibasic acid 19 moles), and therefore, the dispersant obtained by using the polyamide exhibits high water reducing property and slump flow retention. When the chain length of this polyamide is shorter than the case described above (the reaction ratio is less than 0.8 mole), the dispersant obtained by using the polyamide shorter in chain length has markedly decreased slump flow retention. If the chain length is longer than the above (the reaction ratio exceeding 0.95 mole), water reducing property considerably decreases, which is not desirable.
The polyamide polyamine according to the present invention has acrylic acid residue or methacrylic acid residue of 0.25 mole (in the case of a:b:c=1.0:0.8:0.05 (mole)) to 3.6 moles (in the case of a:b:c=1.0:0.95:0.18 (mole)), but the preferable range is 0.5-2.0 moles from the standpoint of effect. When the value is lower than 0.25 mole (for example, in the case of a:b=1.0:0.8 and that quantity ratio of compound c to compound a is less than 0.05), the proportion of the compound A obtained from this ratio in the final copolymer decreases, and property as a cement dispersant is substantially diminished. On the other hand, if it exceeds 3.6 moles (for example, in the case of a:b=1.0:0.95 and that quantity ratio of the compound c to the compound a exceeds 0.18), over formation of the three-dimensional structure of the copolymer is observed and a sufficient effect can not be obtained.
Amount of alkylene oxide to be added to the polyamide polyamine is 0-8 moles per one equivalent of amino residue of the polyamide polyamine. If it exceeds 8 moles, molecular weight of the compound A increases with inevitable decrease in cation equivalent and sufficient effect as the amphoteric polymer expected of the present invention is not obtained. The addition of the alkylene oxide in the present invention is desirable and the amount thereof is preferably 0.5-6.0, most preferably 1.0-5.5, to one equivalent of amino residue of the polyamide polyamine.
Examples of the compound B used in the present invention include acrylic acid ormethacrylic acid, and their sodium, potassium, ammonium, monoethanol amine, diethanol amine or triethanol amine salts, but sodium or ammonium salts are preferable from the standpoints of effectiveness and economical efficiency.
Examples of the compound C used in the present invention include methacrylic acid esters or acrylic acid esters of methoxypolyethylene glycol, methacrylic acid esters or acrylic acid esters of ethoxypolyethylene glycol, methacrylic acid esters or acrylic acid esters of methoxypolyethylene glycol/polypropylene glycol copolymer, and-monoacrylic acid or monomethacrylic acid esters of polyethylene glycol.
Production of the water-soluble amphoteric copolymer in the present invention can easily be carried out using the compound A, the compound B and the compound C by the conventional method in the pertinent art.
Copolymerization ratio of compound A:compound B:compound C in the copolymer of the present invention is in a range of 10-40:10-40:50-80, and is appropriately selected such that the sum is 100 as the weight basis. If the ratio is outside the above range, the effects below can not be obtained.
The water soluble amphoteric copolymer thus obtained in the present invention has the characteristic of having extremely superior water reducing property and prolonged slump flow retention as a cement dispersant, and is possible to exhibit the performance that has not been achieved as cement dispersants heretofore in use or otherwise proposed. These advantages seemed to be brought about by having a nonionic hydrophilic group comprising carboxyl group (anionic group), polyalkylene polyamide group (cationic group) and alkoxypolyalkylene glycol group in the molecular structure of the copolymer, and thus the basic concept of the present invention is in the use of the copolymer having such a unique structure. In particular, the copolymer having specific amide group functioning as cationic radical has not yet heretofore been proposed, and therefore striking effect that has been observed but not predicted is in fact surprising. JP-A 7-33496 discloses the technique in which polyamide polyamine is incorporated as a copolymer component for cement dispersant, however, a copolymer using the polyamide polyamine defined in the technique disclosed by JP-A 7-33496 has the limit in water-reducing property, slump flow retention, hardening and the like when water/cement ratio or water/binder ratio in a concrete is 30% or less, and thus superior water reducing property and slump flow retention observed in the present invention can not be expected.
In general, it is known that use of a polymer type compound having many anionic groups in the molecule is effective as a dispersant in order to disperse substances with positively charged surface such as cement particles as well as to retain its fluidity in the presence of a small amount of water.
It is known that anion moiety of polymer adsorbs positively charged particles and neutralize them, and the polymer thus adsorbed provides good dispersion system by its electric repulsion force of negative charges, and it is also generally discussed that fluidity of dispersion system is likely to be enhanced with stronger electric repulsion force among particles.
It is apparent that sulfonic acid group which is an anionic group functions in, for example, xcex2-naphthalenesulfonic acid/formalin high condensate or the like, and carboxyl group which is an anionic group functions in salt of lower xcex1-olefin/maleic anhydride copolymer or sodium polyacrylate.
Further, it is said that (meth)acrylic acid/alkoxypolyethoxy (meth) acrylate copolymer and the like can exhibit their dispersion and fluidity by that carboxyl group and bulky alkoxypolyalkylene glycol group acting among particles.
However, it is the state of art for these currently available compounds that there is the limit in fluidity effect for an ultrahigh-performance concrete with a small amount of water present, and the problem on slump flow retention can not be solved. Further, it is possible to add an excess amount of water in order to achieve an initial fluidity, but this is out of the question as a concrete for structures as setting becomes extremely slow with acute possibility of poor hardening.
As a result of investigations into various copolymers, the present inventors have finally found the copolymer described in the present invention far superior to the performance of currently available compounds and are trying to elucidate such a mechanism at the present time.
It is considered that the polycarboxyl groups of the water-soluble amphoteric copolymer according to the present invention participates in neutralization of charges as well as an electric repulsion force among cement particles, and it is supposed that the terminal hydroxyl group of the polyamide polyamine group greatly influences in slump flow retention with the cationic group moiety having the specific amide group in the present invention showing some charge regulating action.
Further, it is supposed that carboxyl group, alkoxypolyalkylene glycol group and polyamide polyamine group which constitute the compound of the present invention sufficiently bear their corresponding roles in achieving good effect in the dispersion system, and yet the synergistic action among them have been demonstrating remarkable effect.
Although the amount of the cement dispersant comprising the water-soluble amphoteric copolymer of the present invention to be added varies depending on the compounding conditions including materials used in said concrete, as a general rule, about 0.1-1.5% in terms of the solid content in cement is added. That is, the more dispersant added, the better water reducing property and slump flow retention are. However, setting retardation and in the worst case, poor hardening may be observed if the amount added is too much excess. The way to use the present invention is the same as in currently available general cement dispersants, and the cement dispersant of the present invention is added in the form of a stock solution at the time of kneading concrete or in previously diluted form with kneading water. Alternatively, the dispersant may be added after kneading a concrete or a mortar, and the resulting mixture may again be kneaded to comparable homogeneity.
The present invention also relates to a concrete composition containing said cement dispersant of the present invention. Components other than the cement dispersant described are the conventionally used components for concrete such as ordinary Portland cement, early-strength Portland cement, low heat-moderate heat Portland cements or blast furnace cement for cements, fine aggregates or course aggregates for aggregates, silica fume, calcium carbonate powder or slag powder for admixtures, expanding agent., and water. It is needless to say that the conventional dispersants, water reducing agents, air entraining agents, defoaming agents and the like, other than the dispersant of the present invention, can appropriately be compounded. The compounding proportion of each of these components can easily be determined according to the kind of component selected and objectives.